How to have onTap gestures on Map and MapAnnotation both, without the two interferring with each oth-CodePudding

I have a SwiftUI Map with MapAnnotations. I would like to have an onTap gesture on the Map, so it deselects the selected annotations, and dissmisses a bottom sheet, etc. Also would like to have an onTap gesture on the annotation item (or just having a button as annotation view with an action there), which selects the annotation and do stuff. The problem: whenever I tap the annotation, the map's ontap gesture is triggered too. (When I tap on the map, it only triggers the map's action, so no problems there.) Here's some sample code:

import SwiftUI
import MapKit
import CoreLocation

struct ContentView: View {

   @State var region: MKCoordinateRegion =
   MKCoordinateRegion(center: CLLocationCoordinate2D(latitude: 47.333,
                                                     longitude: 19.222),
                      span: MKCoordinateSpan(latitudeDelta: 0.002, longitudeDelta: 0.002))


   var body: some View {

       Map(coordinateRegion: $region,
annotationItems: AnnotationItem.sample) { annotation  in
           MapAnnotation(coordinate: annotation.location.coordinate) {
               VStack {
                   Circle()
                       .foregroundColor(.red)
                       .frame(width: 50)
                   Text(annotation.name)
               }
               .onTapGesture {
                   print(">> tapped child")
               }
           }
       }
       .onTapGesture {
           print(">> tapped parent")
       }
   }
}

I tap on the annotation, then:

>> tapped parent
>> tapped child

I tap on the map, then:

>> tapped parent

EDIT:

I have tried and didn't work:

make parent action depend on a boolean, which is set to prevent map's action when child is tapped. See in comment: I can only delay the parents action with this, cannot cancel it.
add on custom tap gesture for each, and set .exclusivelyBefore(:) modifier on one of them

CodePudding user response：

Currently one little hack seems to work! I change the onTap gesture to a DragGesture with a minimum distance of 0.

var body: some View {

        Map(coordinateRegion: $region, interactionModes: [.zoom, .pan], annotationItems: AnnotationItem.sample) { annotation  in
            MapAnnotation(coordinate: annotation.location.coordinate) {
                VStack {
                    Circle()
                        .foregroundColor(.red)
                        .frame(width: 50)
                    Text(annotation.name)
                }.gesture(childTapGesture)
            }
        }
        .onTapGesture {
            print(">> tapped parent")
        }
    }
   
    let childTapGesture = DragGesture(minimumDistance: 0).onEnded {_ in
        print(">> Tapped child")
    }
}

and it works! The problem with this solution, is that touching one of the pins while dragging the map, triggers the pin action unintentionally. Thus my answer will not be the accepted one

CodePudding user response：

This seems to me to be a bug, since the default behavior is that only one gesture recognizer fires at a time, see here.
A similar problem occurs in a ScrollView, but there exists a property .delaysContentTouches to solve it, see here. This does unfortunately not exist for a View.
A possible workaround is to delay the parent tap action until it is ensured that no child tap action follows. You could add to your ContentView a @State var childTapTriggered = false and set this var to true if it triggered. Then you could use as parent tap gesture closure something like

DispatchQueue.main.asyncAfter(deadline: .now()   delay) {
  if !childTapTriggered {
       // do parent action
    }
}

EDIT (due to the comment of Gergely Kovacs):

The above workaround does not work, sorry, pls see the comment.
But I tested the following workaround, and it works in my case:

I added to the ContentView a state var:

@State var childTapped = false

On the annotation view (the child), I have the following modifier:

.onTapGesture {
    print(">> tapped child")
    childTapped = true
    DispatchQueue.main.asyncAfter(deadline: .now()   0.1) {
        childTapped = false
    }
}

On the map (the parent) I have the following modifier:

.onTapGesture {
    if !childTapped {
        print(">> tapped parent")
    }
}

Of course this is again a hack, and the delay to reset childTapped to false had to be adjusted right.
Anyway, maybe this solves your problem!